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The Imperatives of Space Industry

~ unavoidable constraints pick designs for future robot-mining & transport ~

Photo by Sam te Kiefte on Unsplash

TL;DR — After we’ve laid a toe-hold on the moon, space industry will accelerate rapidly. Whoever converts capital-equipment into more equipment and infrastructure with the fastest doubling-time will dictate future activities in space. That Capital-into-Capital mandate, and a few physical limitations, narrow-down the viable designs; I go into details below.

Capital Doubling-Time

Futurists muse dubious methods for space industry and transport; convincing us that millions of people would live up there — colonists would rove the surface of Mars. Yet, there is a simple, economical, entrepreneurial problem: “If I spend $100 on robots in orbit here near Earth, and they double themselves every 4 months by gobbling a Near Earth asteroid, then I have $800 at the end of one year, and $6,400 in two years. Will your colonists yield that rate of return?” No.

This is the Capital-into-Capital Mandate — make more stuff that makes stuff, faster than everyone else. Space industry is going to be ruthlessly efficient; whoever finds the faster, cheaper way to double capital will be able to expand a billion-fold. In contrast, as soon as you include humans-on-site, the costs of operation become overwhelming. And, there are immense societal and political issues, from accidents to disputes, independence-minded colonists. Mining companies will just send disposable robots, and avoid the headache. Humans will visit as tourists, in proscribed areas, and they will never be in space for a task. [Any human so skill-delicate that they cannot tele-operate their task would also be so precious that you wouldn’t send them onto a busted nuclear coil-gun, for example. You design to avoid that situation.] Imperative of Space Industry: ROBOTS ONLY.

The Capital-into-Capital Mandate also determines what power sources we will actually use. No, not thorium-heat rockets. Gram-for-gram, the most power, at lowest maintenance, with greatest capacity for scaling and agglomeration, is a solar reflector. Without question, the ability to rapidly re-direct power without capital or fuel loads or infrastructure for all that distance between you, is the absolutely critical superpower of solar reflectors. Only a few pounds of metals, or plastic (mylar), or even layers of glass and ceramics (dichroic mirrors) are all sufficient to beam a few MegaWatts of power from a Mercury-adjacent orbit to almost anywhere, fast. Nuclear power can’t safely pull megawatts from a few pounds of reactor — it’d melt! In fact, those solar reflectors’ power, beamed inwards from all sides, super-heats industrial furnaces which manufacture more of these mirrors. Reflectors cheaply concentrate power unlike chemical, electrical, nuclear sources, as well. Any other industrial activity is a costly distraction, until solar reflector-power is again in surplus.

The Capital-into-Capital Mandate also punishes long-haul transport; any materials on-hand are preferred, over having to import compounds that traveled for months. Even though they are already stocked when you need them, the fact that they had to travel so far will multiply their cost to you. This happens because of a high discounting of the future. What that is, and how it restricts imports, will shape a number of other limitations, as well…

The Discount of the Future

The ‘discount rate’ is a term economists use to describe “how people value income less when they have to wait a long time for it, because they could have made money as interest if they’d had the cash immediately.”

Example: Would you rather have $100 today, or $112 in a year, guaranteed? Turns-out, about half of investors say they’d prefer the $100 today, when offered $112. At $110, most investors pass; at an offer of $115, however, most investors will take the year-long wait for the extra $15, because that’s a BETTER yield than their next best investment. That ‘next best investment’ is what determines the discount rate.

So, if the return on investments suddenly increases astronomically, say ‘doubling ever 4 months’, then you would only pass on “$100 today” if you were offered MORE than $800 in a year — considering that you could take the $100 today, invest in space mining, and have $800 in a year that way. The discount rate would jump from the current ‘12% annual’ to an absurd ‘700% annual’.

Why does that matter? Discounting the future by such a large amount means that “if you’re going to pay me in ten years, it’s basically worthless, because a dollar INVESTED today becomes worth so much more than you’re offering me, by that time.” A trip to the Asteroid Belt, chugging slowly with an ion thruster, is a years-long money pit. It’s only attempted for capturing choice ice-chunks, because the only things the moon and Mercury are missing are volatile compounds. Elements, and their availability, are the next imperative.

Where It’s At

Each possible source of material ascends in difficulty and cost — from the easily-nabbed asteroids that whiz close to Earth (Near Earth Objects), to the moon, then asteroids past Mars, then Mercury. The main barrier is the amount of gravity to operate there, which multiplies equipment requirements, and the gravity-well that must be escaped for each export. The quantity of capital-equipment necessary per mass of payload makes export from gravity-wells a poor investment, with the exception of launching key components from Earth, and rich resorts on Venus. [Rockets are just too capital-intensive to operate for most materials, compared to yields from in-space resources, and so volumes of freight-by-rocket will be low. This is still true when power is plentiful —because one pound of payload escaping a gravity-well requires many pounds of equipment, whichever way you slice it.]

As we access each source of materials, the relative abundances of elements at those locations will pick our designs for us: Near Earth asteroids will provide Silicon and Oxygen in abundance and metals like Iron, Nickel, Cobalt, Aluminum are also common. Some asteroids are Carbon-rich, and precious for that. Our space industry, initially, will be mostly fiberglass, aluminum, ceramics, and magnets. Almost all of that material will be in the space-factories that make more reflectors, which in turn power those factories’ kilns and furnaces. [A single Near Earth asteroid can make enough reflector-surface to beam and concentrate more solar power than all of humanity’s energy budget. Just 10²⁰kg is plenty to match the solar power of the entire Earth. That’ll be top priority.]

And, those reflectors will orbit just past the moon, beaming all that sunlight onto the moon’s ‘dark’ side! Why concentrate more light than Earth’s whole bowl, onto just the far side of the moon? That’s the next imperative: Metabolism vs. Agglomeration.

Concentrated Throughput

Almost every industry is more productive when it is operating at a larger scale (if done properly! yet, it is easier to mis-manage a larger operation, as well…). ‘Agglomeration’, this vast slab-ification of industry, is easier to do in space; infrastructure can be miles-thick in all directions while each strut is filamentous, needing to support only a few gyrations. When your industry can grow to envelope moons, the only real limit to agglomeration is getting rid of the heat you produce.

That’s the metabolic limit that animals reach, as well — elephants’ ears are their attempt to afford getting a little larger without cooking themselves, and most microbes’ inability to radiate heat is what caps their size. Space industries will reach a similar limit, taking the form of dozens-prickled star shapes, to emanate radiant heat while allowing reflectors’ sunlight to funnel into the core. The largest heat-sink will be a fin of pumped gas running up the tether on the far side of the moon — the moon’s orbit tosses a cheap space elevator into ideal position for receiving reflected sunlight, and then shunting heat into the wide vacuum. A ‘Space Elephant-Ear’. No other place in the solar system will process more tons of material per second, until we are cracking Mercury wide open.

Mercury, due to its concentration of metals, and large molten core, will be the real prize. Being the source of materials for a nearly-star-enveloping array of reflectors, Mercury’s pace of mining will dictate the amount of energy that can be beamed to spacecraft hauling materials afar. Beamed power to coil-gun vessels will carry the materials and components that cannot be made at home, and it will simultaneously push an array of spinning magnets on tethers. I’ll explain why that beats other interplanetary bulk transport:

Coil-Gun as A Spacecraft

The next imperative of space industry: NO EXHAUST. All mass is costly to obtain, due to the amount of capital sunk into a time lag gathering that material, and attendant discounting of future returns mentioned previously. Also, because we will use fusion for power as well as the production of unavailable elements, then all matter has a latent, durable value as fusion-fuel and new materials. So, if you expend pounds of Xenon just to haul a single pound of asteroid home, you’ll quickly run out of Xenon, long before you’ve scooped-up Saturn’s moons. All that future utility is lost in the void. Mass is too valuable to throw it away in a rocket or ion thruster! Bulk freight MUST be powered without exhausting material. How?

Let the ‘reaction mass’ that you lob out the rear be a package that you are delivering, by firing it in that direction. Thrust is conserved, so the system is easily twice as efficient as rockets at delivering materials, (many times that, system-wide, when powered by solar reflectors’ beams, with a superconducting ‘quenchgun’ to NASA’s specifications) and each launched package aims to various, far-separated locales, without the whole vessel needing to travel there! The package travels a hundred million miles alone, no capital tied-up in transit. Jeff Bezos would love that last-mile.

What would the actual launches and maneuvers look like? Suppose your coil-gun-vessel fired its cannons behind its direction of orbit; that adds energy to the orbit, and it rises further from the sun, paradoxically slowing its apparent velocity. “Fire behind us = Rise and Slow”. In contrast, by firing in the opposite direction down the coil (it doesn’t really care which way you go…), so that your package is shot out in-front of you, then you will reduce your orbital energy, causing you to dip closer to the sun and speed up! “Fire ahead = Dip and Hasten”. Pretty simple to steer, really.

But, what happens to those launched packages? The ones fired behind are now in a retrograde orbit, and by using only slight tilts of the coil and choice of muzzle velocity, then the package arcs backwards toward its destination — either closer or further from the sun. In contrast, when fired out ahead of the coil-gun-vessel, the package has immense velocity — the sum of muzzle and vessel speeds! It will fly out in a wide parabolic, to the outer edges to grab ice moons full of precious Nitrogen. That volatile element, essential for the high-temperature tooltip strength of Silicon Nitride, among other things, will make those payloads especially profitable.

And, between these miles-long cannons’ undulating orbits, there will be tethered pairs of magnets, looking like taffy-pulls or cartoonishly long barbells. These magnet-twins on a string will be the primary use of Iron from asteroids. Most other materials are a better fit for space-structures than steel, and magnetic elements aside from Iron are in short supply. Neodymium and fancy graphene magic will sit in the high-grade equipment, exclusively.

By tethering these two massive magnets, and spinning them, a toroidal field is formed that pumps ions in its vicinity — a funnel to capture the solar wind. Hydrogen from that solar wind will be stored by combining with the Oxygen abundant during rock-refining, becoming easy and maintenance-free water-ice. [The fusion power available from the Hydrogen in the solar wind is roughly a quarter of the sun’s total power output — so it’s still worth grabbing, especially considering that Hydrogen doesn’t hang-out on rocks often, so the wind is our best source, and it is also the best store of power for fusion…]

Coincidentally, when capturing that solar wind, the magnet-duet will also capture the inertia — they are a ‘Plasma-Magnet Sail’ that can accelerate to the outer moons, while retaining the vast inertia of their long tether’s spin. This helps them to position wide, and their tether-tips, traveling fast enough to grab the packages send by coil-guns, can then re-direct the delivery elsewhere. As much as possible, the inertia of travel is conserved, and power is beamed from Mercury’s reflectors. By recycling power as much as possible, then it is economical to operate at higher velocities, overall. And, because the discount rate of the future is high, then even a slight speed-up in cycle-time is worth an enormous margin. Rockets, ion thrusters, and the like, would all yield a lower Capital-into-Capital Rate. 10⁴⁵kg won’t wait for them.

The Imperatives of Space Industry:

— Turn Capital and Infrastructure into More Capital and Infrastructure, Quickly

— Robots Only

— Build Reflectors Until Demand is Temporarily Saturated

— Future Earnings are Heavily Discounted; All Delays are Expensive due to Opportunity Cost from Rapid Doubling of Capital at home, instead

— Bare Essentials are Imported at a Steep Price, due to Discount Rate, above

— Beamed Power Concentrates at Agglomerated Industrial ‘Chrysanthemums’ that Radiate Heat Quickly to Sustain High Throughput

— Bulk Transport has NO Exhaust; all Reaction Mass Launches are Deliveries, elsewhere

— Iron is Magnets on Tethers to Relay Packages and Funnel Hydrogen as Energy Commodity, Stored as Water

— Recycling Inertia Efficiently will Multiply Power Available toward Higher Velocities, for all mass in transit

— The Discount Rate of Future Earnings Demands Highest Feasible Velocities for Transit; Reflector Power into these, and Chrysanthemum Furnaces

So, just as the O’Neill Cylinder is plainly the best off-world habitat for humans, it seems clear that space-industry will be filled first and foremost with reflectors, coil-gun-vessels, magnetic barbells, and the beam-powered furnaces that make them. Like an egg, or a honeycomb, they are the natural shapes for those purposes.

[Orbital Side-bar: It’s tempting to suppose that all the tethered magnets would end-up flying too far into space —no worries! They can easily launch material that is aimed ‘mostly-forward’ to slow themselves down and dip closer to the sun. And, ‘mostly-forward’ is close enough to the orbit of inner bodies that one of the inner stations can catch a package thrown by the far-away magnets. Catching that package as it whizzes-by would transfer inertia, again — hauling mass from that inner body further outward, which was exactly what was needed to export precious metals from Mercury. Keep cycling that inertia, to multiply its utility. An 80% inertia recapture rate yields 5x kinetic energy sustained in equal mass at each moment, for a given system-power, allowing travel at 5^.5=2.236-times higher velocity!]




where the future is written

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Anthony Repetto

Anthony Repetto

Easily distracted mathematician

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